The present invention relates to a method for connecting two members to each other by means of a third member which is cold-pressed to make a plastic flow into a gap between the connecting surfaces of the two members so as to rigidly connect these members to each other. More particularly, the invention relates to a method suitable for use in connecting two members made of a metal or a plastic for a large torque transmission, e.g. connection between a shaft and a disc, a connection between two sleeves and so forth.
Welding (including soldering), casting and riveting have been known as methods of connecting two members to each other.
As is well known, welding is not suitable for use in connecting members with high precision because members to be connected, as well as the connecting members, are distorted thermally due to the heat generated during the welding. In addition, welding is adaptable only for specific combinations of materials of the members to be connected and the connecting member. Also, it is necessary to select specific material of the welding rod or solder. In addition, welding can provide only a small yield, and require a large scale of equipments. Further, welding is more likely to incur defects in the quality of products due to a possible fluctuation of the working condition.
On the other hand, casting requires large size, complicated equipment, because it necessitates internal chills, rotation prevention mechanism and so forth, in order to ensure a sufficient connecting strength. Further, there is a limit for the selection of the material of the connecting member or the like. In addition, the casting method also suffers a small yield and low precision.
Where the connection between two members is required to withstand a torque which oscillates in two directions, as is the case of connection between a shaft and a fly-wheel of a fly-wheel magneto which is used for the ignition of small-sized internal combustion engine or lighting purposes, riveting is used for connecting them. However, connection by rivets poses various problems. For instance, the diameter of a flange of the boss is rendered large, so as to provide the areas for rivets. At the same time, a useless space or room is required in the axial direction. In addition, the rivets cannot provide an intimate contact of the two members, and the connection is rendered not so reliable.
Press-fitting and caulking have been known as the methods of directly connecting two members. However, press-fitting, can provide only a small connecting force and is less resisting particularly to an impacting force. In addition, it is difficult to obtain sufficiently high strength, when material to be connected is a metal which exhibits small elongation property, e.g. cast steel.
Caulking methods are applicable only to specific materials which exhibit low resistance against deformation. For instance, cast steel and the like cannot be used. Thus, this method cannot provide a sufficiently large connecting strength for all kinds of materials.
A also known is a connecting method in which a connecting member is interposed between two members to be connected and the connected member is plastically deformed. U.S. Pat. No. 3,559,946 shows this method. Referring to this U.S. Patent, a groove having a rectangular section is provided on the connecting surfaces of the two members. A connecting member is inserted between the two members to be connected. The connecting member is pressed so as to be plastically deformed and a part of the connecting member plastically flows into the groove. According to this method, however, since the groove has a rectangular section, the connecting member does not perfectly flow into the groove and there is a gap between the inner surface of the groove and the connecting member. Further, since the connecting force between the two materials to be connected is a frictional force between the flat inner surface of the groove and the surface of the connecting member, it cannot withstand a large torque.